Check out EURO HISTORY/Criminology/GenderStudies for your remaining subject.
this is fact that USA history is short and can be covered within weeks but since many candidates are opting USA history so there are chances that paper could be more rational and demands analytical answers as compared to other history subjects.

As far as scoring trends are concerned, i always say that they are aspirants who outline the scoring trends. One should always keeps ahead the interest of his own for a subject rather than being a victim of these myths. Example: IR in 2017

I am also discouraged over my selection of Accounting&Auditing and leaving IR but this is my firm belief and self-confidence which holds me strong that i can do better with my personal favourite subject A&A.

BEST OF LUCK.